It is known that thin wall articles such as gloves, condoms, sleeves, catheters, balloons, teats, enema tips and other tubular articles can be made from latexes by, for instance, multiple dipping of forms or by use of a coagulant on a form. These methods are widely used for natural latex and for some of the synthetic latexes like nitrile, SBR and others. Increasing human allergy to articles made from natural latex is becoming the main concern of their applicability, but all currently available synthetic dispersions and films based on them cannot match the natural latex. The main deficiencies are the difficulty of obtaining films by ionic deposition (coagulation process), cracking of the films, substantial shrinkage upon formation of the films, poor physical properties of films, and high film toxicity to human skin due to the additives used in the processing step of the synthesis of the polymer.
It is also known that polyurethane elastomers designed for flexible gloves have some very good properties such as tensile strength, puncture resistance, non-toxicity, oil and fat resistance, and breathability. These properties are considerably better than the properties of films obtained from natural latex. The main deficiency of these elastomers is that they are solvent based, with all the accompanying consequences of hazardous manufacturing, environmental pollution and the requirement for high capital investment.
Attempts are continuously made to develop gloves from polyurethanes dispersed in water (PUD). Up to now, films made from these dispersions suffer from low tear resistance, poor elongation of the films and high modulus. In addition, it has heretofore been difficult to make articles by ionic deposition from these dispersions. When these polymers are tailored to be used by ionic deposition, then the formed articles exhibit cracking and severe shrinkage. Plasticization of films to overcome these negative properties results however in sharp lowering of physical properties.
Thus, there remains a need for aqueous dispersions of polyurethane from which gloves and other thin wall articles can be prepared, wherein the articles can be prepared reliably and easily and, once prepared, exhibit physical properties such as higher tear resistance, better elongation and better modulus, and better resistance to cracking and shrinking.